Parkinson’s Disease
Parkinson’s disease is a progressive neurological disorder characterized by the gradual loss of nerve cells in the midbrain that produce dopamine. Dopamine is an important neurotransmitter responsible for controlling movement, coordination, and several other functions of the nervous system.
There are two main categories of Parkinsonian disorders: classic Parkinson’s disease (also known as idiopathic Parkinson’s disease) and atypical Parkinsonian syndromes. Although these conditions may share similar symptoms, they differ in their underlying causes, progression, prognosis, and treatment approaches.
Symptoms of Parkinson’s Disease
The main symptoms of Parkinson’s disease are related to dopamine deficiency and include four characteristic features:
- Slowness of movement (bradykinesia)
- Muscle stiffness (rigidity)
- Tremor, most commonly occurring at rest
- Impaired balance and postural stability, usually in later stages of the disease
In addition to movement-related symptoms, Parkinson’s disease may cause non-motor symptoms, which can appear years before noticeable movement problems develop. These may include a reduced sense of smell, depression and sleep disturbances, including REM sleep behavior disorder.
As the disease progresses, patients may also develop problems with blood pressure regulation, bladder dysfunction, cognitive impairment and, in some cases, dementia. These symptoms are not caused solely by dopamine deficiency. They may also result from changes in other neurotransmitter systems within the brain.
Causes of Parkinson’s Disease
Despite extensive research, the exact cause of Parkinson’s disease remains unclear. Current evidence suggests that the condition may be associated with a combination of factors, including genetic predisposition, oxidative stress, impaired cellular waste-clearing mechanisms, and possible environmental influences.
A key feature of the disease is the progressive degeneration of dopamine-producing nerve cells. As dopamine levels decline, the characteristic symptoms of Parkinson’s disease begin to develop.
Diagnosis of Parkinson’s Disease
The diagnosis of Parkinson’s disease is usually based on a neurological examination and the assessment of characteristic symptoms.
Additional examinations can be helpful, particularly in the early stages of the disease or when there is uncertainty about the exact classification of symptoms. These may include:
- brain parenchyma ultrasound;
- medication-based diagnostic testing;
- nuclear medicine imaging;
- magnetic resonance imaging (MRI) of the brain to exclude other neurological conditions.
Medication-Based Testing
Medication-based tests can help confirm the diagnosis and evaluate potential treatment responses.
These tests may include:
- L-DOPA test
- Apomorphine test
During testing, patients receive a carefully defined dose of medication. The effect on mobility is then assessed before and after administration using standardized clinical criteria.
In patients with significant tremor, a Clozapine test may also be performed. This test helps evaluate whether treatment with clozapine may reduce tremor severity.
Nuclear Medicine Diagnostics
DAT-SPECT is a specialized imaging study used to evaluate the dopamine system within the brain.
This examination can identify changes characteristic of Parkinsonian disorders and help confirm the diagnosis when clinical symptoms are present.
Additional imaging studies may be used when a more detailed differential diagnosis is required:
- FDG-PET – assessment of brain metabolism
- DMFP-PET – evaluation of dopamine receptor function
These methods can help distinguish Parkinson’s disease from atypical Parkinsonian syndromes, including Multiple System Atrophy, Progressive Supranuclear Palsy and Corticobasal Degeneration.
Treatment of Parkinson’s Disease
Treatment is individualized and depends on disease stage, symptom severity, age, and response to therapy.
Neuroprotective Therapy
Early diagnosis is important because it allows treatment to begin at an early stage. One of the major goals of modern Parkinson’s research is to protect nerve cells and slow their degeneration. This approach is known as neuroprotection.
Currently, there are no medications with a proven neuroprotective effect. However, several promising therapies are being investigated in clinical trials.
Medication Therapy
The primary goal of treatment is to compensate for dopamine deficiency.
L-DOPA Therapy
L-DOPA is the precursor of dopamine and remains the most effective medication for treating the motor symptoms of Parkinson’s disease.
Once absorbed, L-DOPA is converted into dopamine within the brain, helping to restore dopamine levels and improve movement.
Over time, some patients may develop motor fluctuations, including periods of reduced medication effectiveness and involuntary movements. For this reason, treatment strategies are tailored individually.
Dopamine Agonists
Dopamine agonists bind to the same receptors in the brain as dopamine and produce a similar effect. These medications are broken down more slowly than dopamine, allowing them to provide longer-lasting and more consistent stimulation of dopamine receptors.
They are available as tablets and transdermal patches.
Additional Medications
Other medications may be used to prolong the effects of dopamine or help restore neurotransmitter balance in the brain, including:
- MAO-B inhibitors
- COMT inhibitors
- Amantadine
Different medications can be combined to optimize symptom control and improve quality of life.
Pump Therapy
When oral medications no longer provide stable symptom control, continuous infusion therapies may be considered.
Available options include:
- Apomorphine pump therapy
- L-DOPA intestinal gel pump therapy
The main advantage of pump therapy is the continuous and even delivery of medication, which helps maintain stable stimulation of dopamine receptors.
Apomorphine is administered through a small pump via a subcutaneous infusion. Alternatively, L-DOPA gel can be delivered directly into the small intestine.
Both approaches can significantly improve mobility and reduce periods of severe stiffness and excessive involuntary movements.
Deep Brain Stimulation (DBS)
If oral medication no longer provides sufficient symptom control and quality of life becomes significantly affected, alternative treatment options such as Deep Brain Stimulation (DBS) or pump therapy may be considered.
A comprehensive evaluation is required to determine the most appropriate treatment strategy for each individual patient.